"But it does mean that trains are running very, very close together - particularly as they approach London.

"If there is the most minor of problem or delay on a train, another train can be thrown off its path or slot on the network by a couple of minutes which can sometimes then snowball a little to five or six minutes late.

"We've identified some issues with the 7.29, with the way it interacts with other services, but the timetable and the capacity demand is so intense that some of the options of what we can do are quite limited."